Hi All, I'm new to USB device driver development. I've mostly done a few LKMs (and an ethernet driver) on 2.6 kernels. And this too was sometime back (around 1.5 yrs!)...so my knowledge on a few things might be rusty! :) I'm working on an embedded board and would like to validate a few assumptions here before proceeding to start work on them. The board is a Compulab CM-X270L (PXA270). This board has USB master as well as a slave port. It's currently running a patched 2.6.16 kernel (the patch is from Compulab). It runs Compulab's Debian distribution - "Debian GNU/Linux 3.1". We need to use the board as a USB slave to a machine which has a USB master (root hub). This machine runs a proprietary OS and we do not have access to it's source code and/or any other means to access it's internals. This proprietary OS supports the following USB classes: * CDC-ACM: Full ACM specs * CDC-ECM: The USB host side diver on the OS, only works with one particular USB-ethernet dongle (say chip-X). So I'm guessing the OS does not support the full ECM specs. We need to use the board as a slave and test it's interoperability with the host for the above mentioned USB classes. I plan to do the following: 1) CDC-ACM: Compile the USB gadget serial driver as a LKM for the board. If the module loads successfully, connecting the slave port to the host should make it (the slave), enumerate successfully as an ACM device. 2) CDC-ECM: This one's a bit tricky! I understand that the ethernet is implemented in drivers/usb/gadget/ether.c. But, since the host side driver is written to work with a particular chipset, will it work "AS IS" with the ethernet gadget driver? Also, in case it doesn't work, can I tweak the gadget driver to make it work/enumerate correctly with the host? Basically I'll be "faking" the chip in s/w. Also, how can I verify that the kernel has recognized the USB slave device? During kernel configuration, we can choose gadget support as a module. Is there a separate module that needs to be present for gadget support or will individual gadget drivers themselves provide this functionality? The following link states that the USB device functionality is not supported in 2.6.16 kernels: http://www.compulab.co.il/mediawiki/index.php5?title=Linux_Kernel_for_CM-X270#USB_device But if I get the patches mentioned in the link and compile them as modules, then can I enable the USB device functionality? Another pain-point is the fact that I can't re-flash the kernel on the Compulab board with a newer version (I think 2.6.24 has support for USB device). This is because the board directly boots up the kernel and does not stop at the prompt. I've followed the procedure mentioned here: http://www.compulab.co.il/mediawiki/index.php5?title=Getting_started_with_Linux_on_CM-X270#Image_installation but this doesn't seem to work, the bootloader (ARMMon) still boots the kernel directly! :( Any clues as to how to circumvent this problem? Any suggestions are welcome. Thanks for your time. Regards, -mandeep -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
